<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    html{
        --color:#ccc;
        --lenght:100px;
    }
    *{
        margin: 0;
        padding: 0;
    }
    .box1{
        width: calc(100px * 2);
        height: var(--lenght);
        background-color: var(--color);
    }
    .box2{
        width: var(--lenght);
        height: var(--lenght);
        color: var(--color);
    }
    .box3{
        width: var(--lenght);
        height: var(--lenght);
        border: 1px solid var(--color);
    }
</style>
<link rel="stylesheet" href="./index.css">
<body>
<div class="box1">111</div>
<div class="box2">222</div>
<div class="box3">333</div>
</body>
</html>
